A 50% reduction of chemical fertilizers for watermelon production due to the application of animal feces-based compost

The dose of animal feces-based compost for a 50 % reduction of chemical fertilizers, effects of the compost application on soil chemical and physiological characteristics, and watermelon weight and quality were investigated. 1. The animal feces-based compost was composed of cattle feces mixed with wood chips, swine feces and poultry feces with a proportion of 5 : 4 : 1. The compost was fermented for 8-9 months before application. EC of the compost was 7.4 dS/m (1:10). The content of N, P2O5 and K2O in the compost was 0.8 %, 1.6 % and 1.0 %, respectively. Inorganic nitrogen amount was 19 mg/100 g. C/N ratio was 20. 2. The compost application with a dose of 2t/10a could induce a 50 % reduction of conventional nitrogen application from 10 kg/10 a to 5 kg/10 a. 3. The continuous application of the compost increased the fruit weight of watermelons. 4. In the case of 5 kg N/10 a, the application of 1t compost/10 a could substitute 3 kg of nitrogen. 5. The continuous application of the compost increased contents of calcium, magnesium, potassium, phosphoric acid, available nitrogen, total carbon, and total nitrogen and also base exchange capacity in the soil. However, soil electric conductivity was little changed. On the other hand, the soil porosity and apparent density were increased. 6. The increased soil electric capacity, nitrate nitrogen content and potassium content by applying 1 t compost were 0.04 dS/m, 2.5 mg/100 g and 17 mg/100 g, respectively. 7. Five kg of nitrogen from chemical fertilizers in combination with the application of Z t compost increased soluble solids of watermelon fruit from 11.3 % (Brix) to 12.1 %. 8. In the case mentioned in No.7, the amount of nitrogen absorption by watermelons was 7.8 kg/10 a, of which, 2.1 kg was from the compost, 1.3 kg from the chemical fertilizer and 6.0 kg from the soil. 9. The utilization coefficient of nitrogen from chemical fertilizer and compost was 28 % and 12 %, respectively. 10. The concentration of nitrate nitrogen in the soil solution of 10 kg of nitrogen application from chemical fertilizer or 6 t compost application was 4 or 5 ppm in the depth of 60 cm. 11. The standard of the application amount of nitrogen from chemical fertilizers and the compost was worked out to produce 3 L grade fruit of watermelons. Before transplanting watermelon seedlings, the application level of nitrogen from chemical fertilizers and dose of the compost could also be determined based on the available nitrogen content in the soil.